It is well known in the art that the supporting structure for pile driving hammers may be angularly positioned so as to drive pile on a slope or batter. Commonly, this is accomplished through the use of various apparatus for tilting the frame in which the hammer is supported. This frame frequently is supported by the boom of a crane such as in U.S. Pat. Nos. 3,734,435 and 3,888,317. Such cranes and their angularly disposed booms occupy substantial space and are not readily adapted to disposition on offshore platforms where space is limited; but the need for pile driving operations nevertheless is present. Frequently such pile driving operations are carried on offshore by disposing the crane and angulated boom on a derrick barge or the like. In such situation, there is no space occupied on the deck of the platform itself, but the derrick barge is very expensive to use. However, as disclosed in my earlier filed application, Ser. No. 765,918, there is shown a method for establishing a movable pile driving rig on the platform itself in order to drive pile and conductor pipe in a predetermined pattern and in the absence of a derrick barge or the like. In that case, it becomes imperative to occupy as little space as possible on the deck of the platform, while at the same time providing for angular adjustment of the lead over a broad range of angles.
Driving operations are commonly carried out from the upper deck of an offshore rig. The upper deck stands a substantial height above the water, as much as sixty feet or more. Therefore, the hammer can drive the pipe only to the level of the upper deck. The structural configuration of the rig further provides for a lower deck, frequently known as the cellar deck, this deck being commonly at a level or forty or more feet above the water. Also, there may be a jacket level proximate the surface of the water at perhaps ten or so feet above. Boat bumpers are frequently attached at the jacket level so that service vessels can tie up to the rig. Since the hammer can drive pile and pipe only to the upper deck, there frequently exists a residual length of pipe above the water after the pile or pipe has been driven to depth this being due to the fact that the hammer can only operate to the level of the upper deck. Therefore, the residual length of pipe must be cut off at some predetermined level in order to attach a Christmas tree or other production equipment. The cutting step is time consuming and, therefore, expensive.